The various subprojects are designed to examine the detection, growth and regression of tumors by means of new radiopharmaceuticals. The pharmaceuticals, carrying detectable radiolabels, will be designed with one or more principles in mind. Some will act as active site-directed enzyme inhibitors. Others will be analogues of substrates for known metabolic pathways. Still others will depend upon physicochemical properties to achieve selective localization. We will examine the kinetic properties of these materials in normal and neoplastic tissues, as well as the "equilibrium" concentrations. Excreta will be studied to determine if the radiopharmaceuticals have been metabolized, and to identify the new metabolites. Great effort will be made to study the distribution of these new materials upon their introduction via a number of routes in vivo. BIBLIOGRAPHIC REFERENCES: Spencer, R.P.; Sziklas, J.J.; Delany, F.: Unusual scan presentations of splenic rupture. Conn. Med. 40:456-457, 1976, (July). Spencer, R.P.; Atkins, H.L.; Richards, P.; Klopper, J.F.; Srivastava, S.C.; Meinken, G.E.; Som, P.: Regional hematocrit: theory, results with phantoms and initial human studies. The Physiologist 19:375, 1976 (Aug.).